<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <script>
        // let a = 123;
        // const b = 456;
        // var c = 657;
        // function fn(){}

        // function abc(a){
        //     let a = 789
        // }
        // abc(789)


        let a = 123;
        let b = '123';
        let c = [1, 2, 3];
        let d = {
            name: 123
        }
        let f = () => {

        }

        // let fn = () => {

        // }

        // console.log(fn);

        function f1(fn) {
            // console.log(fn);
            // let fn=()=>{

            // }           
            // fn(123)
            fn((num2) => {
                console.log("内部函数");
                console.log(num2);

            })
        }

        f1((num) => {
            console.log("啦啦啦");
            console.log(num);

            num(456)
        })
    </script>
</body>

</html>